URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 640
NWS Storm Prediction Center Norman OK
945 PM CDT Tue Sep 1 2026

The NWS Storm Prediction Center has issued a

* Severe Thunderstorm Watch for portions of 
  Northwest into North-Central Iowa
  Southwest into South-Central Minnesota
  Far Northeast Nebraska
  Extreme Southeast South Dakota

* Effective this Tuesday night and Wednesday morning from 945 PM
  until 500 AM CDT.

* Primary threats include...
  Scattered damaging winds likely with isolated significant gusts
    to 75 mph possible
  Scattered large hail and isolated very large hail events to 2
    inches in diameter possible
  A tornado or two possible

SUMMARY...Severe thunderstorm currently moving through extreme
southeast South Dakota is expected to continue northeastward
tonight, tracking through southwest Minnesota and northwest Iowa.
Strong wind gusts from 65 to 75 mph are possible with this storm.
Additional thunderstorms are development across south-central
Minnesota. Some large hail is possible with these storms over the
next hour or two. A lone supercell is also progressing northeastward
across far northeast Nebraska, with an attendant threat for damaging
gust and large hail it is gradually moves northeastward.

The severe thunderstorm watch area is approximately along and 45
statute miles north and south of a line from 40 miles north
northwest of Sioux City IA to 35 miles north northeast of Mason City
IA. For a complete depiction of the watch see the associated watch
outline update (WOUS64 KWNS WOU0).

PRECAUTIONARY/PREPAREDNESS ACTIONS...

REMEMBER...A Severe Thunderstorm Watch means conditions are
favorable for severe thunderstorms in and close to the watch area.
Persons in these areas should be on the lookout for threatening
weather conditions and listen for later statements and possible
warnings. Severe thunderstorms can and occasionally do produce
tornadoes.

&&

OTHER WATCH INFORMATION...CONTINUE...WW 638...WW 639...

AVIATION...A few severe thunderstorms with hail surface and aloft to
2 inches. Extreme turbulence and surface wind gusts to 65 knots. A
few cumulonimbi with maximum tops to 500. Mean storm motion vector
24035.

...Mosier